Authors José Alexandre Borges Valle, Rita de Cássia Siqueira Curto Valle, Andrea Cristiane Krause Bierhalz, Fabricio Maestá Bezerra, Arianne Lopez Hernandez,
Biopolymeric chitosan is considered a promising encapsulating agent for textile applications due to its biocompatibility, lack of toxicity, antibacterial activity, high availability, and low cost. After cellulose, it is nature’s most important organic compound. Also, chitosan has unique chemical properties due to its cationic charge in solution. Microencapsulation technologies play an important role in protecting the trapped material and in the durability of the effect, controlling the release rate, The application of chitosan microcapsules in textiles follows the current interest of industries in functionalization technologies that give different properties to products, such as aroma finish, insect repellency, antimicrobial activity, and thermal comfort. In this sense, methods of coacervation, ionic gelation, and LBL are presented to produce chitosan-based microcapsules and methods of textile finishing that incorporate them are presented, bath exhaustion, filling, dry drying cure, spraying, immersion, and grafting chemical. Bio-based polymers have emerged as a potent solution to replace petroleum-based polymeric materials and reduce dependence on the crude oil reserve. Besides, many of the existing bio-based polymers can be biodegradable; in particular, natural bio-based polymers, among which there are the polysaccharides. Polysaccharides are highly available and have a low cost, in addition to having excellent properties, such as biodegradability, nontoxicity, and good biocompatibility. There is a diversity of polysaccharides, widely used in different areas of knowledge, being cellulose and chitosan (CH) the most common on earth. CH, fully or partially deacetylated form of chitin deriving of organisms such as fungi, crustaceans and wasp (Black Soldier FlyHermetia illucens), has the advantages of to be a nontoxic, rich and wide variety of sources, low cost, easy film formation, good biocompatibility, and enzymatically biodegradable. In addition, many studies seek to improve its solubility and antimicrobial capacity (quaternization and carboxylation) through changes in the structure and addition of compounds to it, maintaining its original biodegradability and biosafety, causing the amount of research to only increase. Much attention also has been given for the use of CH as polymer shell of the microcapsules and also as matrices, conform de Arruda et al. these matrices present features that can be used in the delivery of bioactive compounds, for example.5 As shell can be application on textile substrates. Textile fibers are mostly anionic and CH for being the only cationic polymer already has an ionic affinity. In general, the microcapsule consists of a functional barrier between the core (solids, liquids or gasses compounds, or a mixture of these) and the wall material to avoid chemical and physical reactions and to maintain the biological, functional, and physicochemical properties of the core materials. Today, there are many kinds of microencapsulation processes: emulsification, spray-drying, coaxial electrospray system, freeze-drying, coacervation, in situ polymerization, extrusion, fluidized-bed-coating, and supercritical fluid technology. There is a lot of research working with this theme, due, among other reasons, microencapsulation technique versatility to be applied in a wide range of fields. Some areas that it was detected the microcapsule using: perfume, cosmetic, and personal care, food, pharmaceutical and medicinal treatment, Pest and insect repellency, environmental recovery, construction, and textile. Textile materials have permeated areas beyond the traditional use for dressing people and homes. The cited studies can be adjusted to incorporate CH microcapsules to textiles to provide special characteristics as extra protection in adverse environmental, comfort, specific resistances, beauty, and so on. The new attributes change the performance, demands of consumers, and expand the industrial competitiveness. There are many manners to convert normal textile into one with functional proprieties, the advances in polymer science support the increment of the use of coatings. In this context, microencapsulation is a commercially successful technology for functional textile coatings, mainly for drug delivery, as well as in uses in civil construction, containment of barriers, hospitals, as a carrier for cosmetics, and so on. The active principle or core of the capsule is the substance that wishes to encapsulate. Generally, the active compounds are chemically unstable and susceptible to degradation, particularly when exposed to oxygen, light, moisture, heat, and pH variations or it has some features, as fast release, low solubility, poor bioavailability, high volatility, and some toxicity that is interesting to change in the medium. The shell is the most effective approach to improve stability is to form a barrier between the active principle and the external environment. Then, the wall, shell, or encapsulating agent, of the microcapsule, in addition to the structuring function, serves to protect and isolate the compound from the external environment. It is desirable that they shall materially has no reactivity with the active ingredient, be inexpensive, and show consistent properties during storage. Depending on the kind of wall material and its inherent characteristics, the compound is released from the wall material via various mechanisms such as swelling, dissolution, or degradation. Depending on the rate of these mechanisms, release can occur over various periods. Different materials can be selected from synthetic or natural polymers, as waxes and lipids, proteins, carbohydrates, gums, and other polymers classes. The choice of wall materials depends upon several factors including expected product objectives and requirements; nature of the core material; the process of encapsulation; economics and whether the coating material appropriated for de use. Crosslinkers are compounds applied to improve the physical properties and stability of the microcapsules and efficiency of encapsulation. However, crosslinkers are also used for the connection of the microcapsules with the textile substrate. Some cross-linking agents used for microcapsules are; Tripolyphosphate (TPP), glutaraldehyde, genipin, transglutaminase, tannic acid, urea, and so on, and for the connection between the capsules and the textile, citric acid (CA), and 1, 2, 3, 4-butanetetracarboxylic are employed. Finally, there are surfactants widely used in the preparation of microcapsules that present amphiphilic behavior, which are Tween (8, 20, 40, and 80), Span (20, 80, and 85), SDS, polyvinyl alcohol (PVA), polyglycerol polyricinoleate (PGPN), lutensol, and so on. In the system, surfactants, when used, produce micelles, which are supramolecular arrangements possessing a hydrophobic central core and a hydrophilic crown. The entropy reduction with thermodynamically unfavorable interactions between the lipophilic surfactant tails and water molecules causes the self-assembly in larger molecular organizations when the surfactant concentration exceeds the critical micelle concentration.21 The surfactant can control the particle size and agglomeration,28 also it helps to reduce molecular interactions of chemical groups in the particle surface (van der Waals, hydrogen bonding, or hydrophobic interactions). In the sequence of construction of the articles, it is presented a series of capsule formation processes. The processes most presented in the literature are complex coacervation, ionic gelation, layer-by-layer (LBL), emulsification, spray drying, and so on. Once the active ingredient is encapsulated, it is necessary to characterize the microcapsule. The analyzes that are performed refer to the material of the wall and the nucleus of the microcapsule, these analyzes are: particle size, morphology, scanning electron microscopy, Fourier transform infrared spectroscopy, surface property, zeta potential, differential scanning calorimetry, permeability, transmission electron microscopy, viscosity, and so on with the purpose of determining particle size and morphology, state of aggregation of molecules, surface isoelectric points, functional groups, thermal stability, among others. And the last step is how to apply to the textile substrate. The most popular methods of application are bath exhaustion, padding, pad-dry-curing, spraying, dipping and chemical grafting, and so on. Regarding the textile application of microcapsules, there are many purposes for them, for example, antimicrobial, antioxidant, UV-protection, insect repellent, cosmetic, medical, thermal regulation, and so on.
